This application is based on and claims priority to Japanese Patent Application No. 2001-190173, filed Jun. 22, 2001 the entire contents of which is hereby expressly incorporated by reference.
1. Field of the Invention
The present invention relates generally to an engine control system for an engine, and more particularly to an improved engine control system for adjusting the camshaft timing and fuel injection amount.
2. Brief Description of Related Art
Engines typically incorporate an engine management system. The engine management system commonly uses a computer to control a fuel injection system.
Operator demand for smooth running, highly responsive engines with improved fuel economy can be addressed with engine management systems incorporating adjustable camshaft timing mechanisms. The ability to adjust the camshaft timing allows for the engine management system to better operate the engine during various conditions such as a heavy acceleration or deceleration. Adjustable camshaft timing mechanisms also allows high performing engines with aggressive camshafts to operate better over wider engine operating ranges.
Due to highly variable engine operating dynamics, some adjustable camshaft timing mechanisms fail to adjust the camshafts to the optimal operating camshaft timing value requested by the engine management system. Sudden aggressive acceleration or deceleration periods can create an internal engine operating environment so dynamic that many adjustable camshaft mechanisms cannot adjust the camshaft timing quickly enough to provide an optimal camshaft timing setting allowing the engine to perform to its potential.
One aspect of the present invention is to provide an adjustable camshaft timing strategy, which provides the optimal engine response desired by compensating for the mechanical limitation of an adjustable camshaft timing mechanism through manipulation of the fuel injection amount and/or timing.
Another aspect of the present invention includes the discovery that deviations between the actual camshaft timing and a more theoretically optimal camshaft timing can cause air flow variations which thereby cause rich and lean variations in the air-fuel mixture. It may be possible to detect such air-flow variations with relatively more precise and expensive air flow meters, e.g., moving-vane, heated-wire, and Karman Vortex, and to use the output of these meters to control fuel injection. However, the additional expense of such air flow meters can be impractical in certain applications. Additionally, these air flow meters are vulnerable to water damage, a characteristic incompatible with certain applications, such as, for example, but without limitation, marine environment applications.
Another aspect of the present invention is that is that the lean and rich conditions caused by the VVT behavior can be satisfactorily predicted by comparing the actual camshaft timing to the more theoretically optimal camshaft timing. Thus, the fuel amount delivered to the engine can be adjusted to compensate for the predicted lean and rich conditions corresponding to differences detected between the actual and optimal camshaft timing.
In accordance with another aspect of the invention, an engine includes an engine body having at least one variable volume combustion chamber and at least one intake port opening into the chamber. The engine also includes an induction system communicating with the intake port and an intake valve being moveable to regulate communication between the induction system and the combustion chamber through the port. A camshaft drives the intake valve. At least one fuel injector is configured to supply fuel to the combustion chamber. A fuel injector control module is configured to drive the at least one fuel injector. A variable valve timing mechanism is configured to vary a position of the camshaft to vary a timing of actuation of the intake valve. A sensor is configured to sense a position of a camshaft and to generate a signal indicative of the camshaft position. A variable valve timing mechanism control module communicates with the sensor and is configured to determine a first camshaft timing and to control the variable valve timing mechanism to at least approximate the first camshaft timing. The fuel injection control module is configured to adjust a fuel injection amount based on a deviation of the signal and the first timing.
In accordance with a further aspect of the invention, a method for controlling an engine includes driving a variable camshaft timing mechanism to adjust a camshaft timing according to at least an approximation of a first camshaft timing value. The camshaft timing of the engine is detected. The method also includes delivering a fuel amount to the engine, adjusting the fuel amount according to a difference between the detected camshaft timing and the first camshaft timing value.
In accordance with yet another aspect of the present invention, an engine includes an engine body defining at least one combustion chamber. A crankshaft is rotatably journalled at least partially in the engine body. At least one an intake valve being mounted to the engine body so as to reciprocate therein. A camshaft is rotatably journalled by the engine body and configured to drive the at least one intake valve to reciprocate. The engine also includes a camshaft position sensor and a variable valve timing mechanism configured to adjust an angular position of the camshaft relative to an angular position of the crankshaft. A fuel injector is configured to deliver a fuel amount to the engine body for combustion in the combustion chamber. A fuel injection control module is configured to adjust the fuel amount delivered by the fuel injector. A variable valve timing control module is configured to determine first and second camshaft timing values. The variable valve timing control module is also configured to drive the variable valve timing mechanism according the first camshaft timing value. The fuel injection control module is configured to adjust the fuel amount according to a difference between the second camshaft timing value and a camshaft timing corresponding to the position of the camshaft detected by the sensor.